JPH10316447A - Optical glass - Google Patents

Abstract

(57) [Summary] A refractive index (nd) is 1.50 to 1.60,
An Abbe number (νd) having an optical constant in the range of 60 to 75, and having excellent ultraviolet transmittance. SOLUTION: This optical glass has the following composition by weight percent, P ₂ O ₅ is 50 to 80, and SiO ₂ is 1 to 5
And Al ₂ O ₃ is 5 to 20; B ₂ O ₃ is 0 to 5;
¹ ₂ O is 0 to 20, with R ² O is 0 to 40, As ₂ O ₃ or Sb ₂ O ₃ content _of at 0.1 to 0.5, F ₂ is 1-5, provided that, R ¹ ₂ O is Li ₂ O, Na ₂ O and K ₂ O
At least one selected from the group consisting of: or a combination of two or more thereof, wherein R ² O is MgO, C
At least one selected from the group consisting of aO, SrO, BaO and ZnO, or a combination of two or more thereof, F ₂ (fluorine) is contained in an oxide, Is substituted with fluorine ions and exists as a fluoride, has a refractive index of 1.5 to 1.6, an Abbe number of 60 to 75, and has excellent ultraviolet transmittance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical glass having a low refractive index and a low dispersion, and particularly having a high ultraviolet transmittance.

[0002]

2. Description of the Related Art The refractive index (nd) is from 1.50 to 1.60.
Glass having an optical constant such that the Abbe number (νd) is 60 to 75 with a low refractive index of P ₂ O ₅ −
_{B 2 O 3 -Al 2 O 3} -R 1 2 O-R 2 O as the phosphate crown glass having a composition is known (literature:
Glass Composition Data Book 1991, published by Japan Glass Products Manufacturers Association, p. 100 Special Phosphate Crown Glass P
KS1). For example, the composition of the optical glass in this document is as follows: P ₂ O ₅ is 70.4, B ₂ O ₃ is 4.0, Al ₂
O ₃ is 9.0, K ₂ O is 11.6, MgO is 4.0, A
s ₂ O ₃ was 1.0. The refractive index (nd) of this optical glass is 1.518 and the Abbe number (νd) is 6
9.6. Wherein, R ¹ ₂ O is an alkali metal oxide contained in the glass, R ² O is one or both of the alkaline earth metal oxides and zinc oxide contained, will be represented respectively.

[0003] Glass having a refractive index and Abbe number as described above has excellent properties without devitrification.

[0004]

However, in the phosphate crown glass containing P ₂ O ₅ as a main component as described above, the content of P ₂ O ₅ in the glass component generally increases. The elution of platinum, which is the material of the melting tank used, into glass is promoted. The eluted platinum reduces the transmittance of the glass in the ultraviolet region. In addition, the elution of platinum is promoted by an increase in the dissolution temperature, and the elution is remarkable under a reducing atmosphere.

However, in order to obtain a glass having the above-mentioned optical constant and stable against devitrification, the content of P ₂ O ₅ must be sufficiently large.

[0006] It is naturally conceivable to use a crucible of quartz or the like instead of the platinum crucible for the manufacture of glass, using a quartz crucible when would be SiO ₂ melts into the glass, resulting homogeneity good glass minor I can only get it.

[0007] If a platinum crucible is used, mass production is possible. For this reason, glass is currently manufactured mainly using platinum crucibles.

[0008] One of the factors that reduce the transmittance of the glass in the ultraviolet region is the use of an excessive amount of a defoaming agent. Instead of using a defoamer as a method of removing bubbles generated in the glass, there is a method of lowering the viscosity of the glass melt, such as increasing the melting temperature, increasing the alkali component, and reducing the viscosity increasing component such as aluminum oxide. Conceivable. However, the decrease in the transmittance due to the incorporation of platinum into the glass is remarkable, and the chemical durability may be deteriorated. Therefore, the refractive index (nd) of the conventional crown phosphate glass of the composition system is low. It was difficult to obtain an optical glass having an optical constant of 1.50 to 1.60, an Abbe number (νd) of 60 to 75, and a high transmittance in the ultraviolet region.

Therefore, in consideration of the above-mentioned problems, the refractive index (nd) satisfies the range of optical constants of 1.50 to 1.60 and Abbe number (νd) of 60 to 75, The appearance of an optical glass having high transmittance in the ultraviolet region has been desired.

[0010]

The inventors of the present invention have conducted intensive studies, and as a result, have found that phosphoric acid P ₂ O ₅ , silicate SiO 2
_2, oxide of aluminum Al ₂ O ₃ as essential components, the boric acid is a conventional essential components B ₂ O ₃ and alkali metal oxides R ¹ ₂ O optical glass composition according to any component, have the desired optical constants However, they have found that a crown phosphate glass having high transmittance in the ultraviolet region and excellent stability against devitrification can be obtained, and the present invention has been accomplished.

[0011] Optical glass is the following composition in percent by _{weight, P 2 O 5 50~80 SiO 2} 1~5 Al 2 O 3 5~20 B 2 O 3 0~5 R 1 2 O 0~20 of the invention R _² O 0~40 As ² O ₃ or Sb ₂ O ₃ 0.1~0.5 F ₂ 1~5 However, R ¹ ₂ O is selected from the group of Li ₂ O, Na ₂ O and K ₂ O At least one or two of these
One consists more thereof, R ² O is MgO, Ca
At least one selected from the group consisting of O, SrO, BaO, and ZnO, or a combination of two or more thereof, the above-mentioned fluorine F ₂ is an oxide, and a part of oxygen ions of the oxide is It is substituted with fluorine ions and exists as a fluoride, has an optical constant of a refractive index (nd) of 1.50 to 1.60, an Abbe number (νd) of 60 to 75, and transmits ultraviolet light. It is characterized by having excellent properties.

The above composition ranges have been found by experimental chemistry, and the reasons for limiting the range of each component are as follows.

First, phosphoric acid P ₂ O ₅ is a glass-forming oxide and is an essential component for lowering the refractive index of glass. However, in order to maintain stability against devitrification, it is contained in an amount of 50% by weight or more. In order to maintain the chemical durability and suppress the elution of a large amount of platinum, the content is preferably 80% by weight or less.

Next, SiO ₂ silicate is an essential component that lowers the refractive index of the glass and suppresses the elution of phosphoric acid P ₂ O _5. However, when SiO ₂ alone is used, an unmelted substance is formed on the surface of the glass melt. Easy and requires an increase in melting temperature. However, if introduced as a fluorine compound (for example, SiF ₂ ), the content can be increased without increasing the melting temperature. However, in order to maintain stability against devitrification and prevent deterioration of glass homogeneity due to volatilization of a large amount of SiF ₂ , the content of silicic acid is preferably 1% by weight or more and 5% by weight or less.

Aluminum oxide Al ₂ O ₃ is generally an essential component for improving the chemical durability of glass.
The effect is remarkably exhibited at 5% by weight or more. Further, in order to maintain stability against devitrification and not to increase the viscosity of the melt which causes an increase in the melting temperature, the content is preferably 20% by weight or less.

By adding an appropriate amount of another substance as an optional component in addition to the above essential components, the optical constant of the glass can be made closer to a desired value, and the melting temperature is lowered to facilitate melting. Therefore, the adverse effect on the glass due to the erosion of the crucible can be reduced.

As an optional component added for this purpose, boric acid B ₂ O ₃ is a component that suppresses volatilization of phosphoric acid P ₂ O ₅ , but in order to maintain chemical durability, it is not more than 5% by weight. It is preferable to set the content.

The alkali metal oxides ^{_{R 1 2 O (Li 2 O}} + N
a ₂ O + K ₂ O) is a component that can lower the melting temperature and lower the refractive index. The content is preferably 20% by weight or less so as not to increase (the glass melt is separated into liquid phases having different components and cannot be mixed). As the alkali metal oxide, one of Li ₂ O, Na ₂ O and K ₂ O may be selected and contained, or two or more of these may be selected and contained. Note that Li ₂ O + Na ₂ O + K ₂
O is, R ¹ ₂ O is a component Li ₂ O, Na ₂ O and K ₂ O
Is expressed by the total content of

R ² O (MgO + CaO + SrO + BaO + Zn) which is an alkaline earth metal oxide and zinc oxide
O) is generally large glass forming ability, but there is a component for improving the stability against devitrification, phosphoric acid P ₂ O ₅
In consideration of the content of, the content is preferably 40% by weight or less so as not to increase the refractive index of the glass. Further, as the alkaline earth metal oxide and zinc oxide, MgO, Ca
One of O, SrO, BaO and ZnO may be selected and contained, or two or more of these may be selected and contained. In addition, MgO + CaO + SrO + Ba
In O + ZnO, R ² O is composed of components MgO, CaO, Sr
It means that it is represented by the total content of O, BaO and ZnO.

Fluorine F ₂ is a component that lowers the melting temperature and suppresses the elution of phosphoric acid P ₂ O _{5 on} the glass surface. However, in order to obtain the effect, it must be contained in an amount of 1% by weight or more. . Further, in order to maintain stability against devitrification and to prevent deterioration of homogeneity due to a large amount of volatilization, the content is preferably 5% by weight or less.

Arsenic (III) oxide As ₂ O ₃ or antimony (III) oxide Sb ₂ O ₃ is used as a defoaming agent, but it must be contained in an amount of 0.1% by weight or more in order to sufficiently defoam. . Further, the content is preferably set to 0.5% by weight or less, since it causes the refractive index to increase and lowers the internal transmittance of the glass.

In the present invention, fluorine F ₂ exists as an oxide in an oxide in which some oxygen ions of the oxide are replaced by fluorine ions. Fluorine introduced into the glass as a fluoride is a component that contributes to improvement in chemical durability and reduction in melting temperature as described above within an appropriate amount.

Preferred examples of the composition of the optical glass of the present invention include the following composition examples.

By weight%, P ₂ O ₅ is 71.6, SiO ₂
2.0, Al ₂ O ₃ 16.4, K ₂ O 6.7, C
aO is 1.2, As ₂ O ₃ is 0.1, F ₂ is 1.9,
R ¹ ₂ O is K ^₂ O6.7, R ₂ O is CaO1.2.

The optical glass having such a composition has the above-mentioned desired optical constant, and is excellent in stability against devitrification and chemical durability. It also has excellent transmittance in the ultraviolet region.

Further, the optical glass 10 mm
80% value of internal transmittance (τ80% (nm)) is 330n
m or less.

This value is the wavelength of light incident on the glass having a thickness of 10 mm at which the internal transmittance of the glass becomes 80%. Here, the smaller the value, the higher the transmittance in the ultraviolet region. Is shown. The high transmittance in the ultraviolet region means that in the present invention, the transmittance in the ultraviolet region is excellent. The optical glass of the present invention can set the 80% value of the 10 mm internal transmittance to 330 nm. That is, since the wavelength is 330 nm at the maximum, the wavelength can be made lower than that of the related art, and the transmittance in the ultraviolet region can be increased.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to working composition examples. It should be noted that the materials used and the amounts thereof, other numerical conditions, and processing methods mentioned in the following description are merely examples within the scope of the preferred invention, and therefore, the invention is not limited thereto. .

The optical glass of this example was manufactured by the following method.

First, corresponding oxides, carbonates, nitrates, fluorides, these compounds and the like are used as raw materials of the respective components, and they are weighed at desired ratios, respectively.
This was mixed well in a powder or a solution to obtain a prepared raw material. For each raw material, a transition metal as an impurity, particularly one having an iron content of 1 ppm or less was used. Next, this is put into a platinum or quartz crucible in an electric furnace heated from 1000 ° C. to 1350 ° C., melted and clarified.
Stir to homogenize. Thereafter, it was cast into a pre-heated iron mold and gradually cooled.

The composition (weight percent), optical constants (refractive index (nd), Abbe number (νd)) of the optical glass examples of the present invention, and the internal transmittance of the glass of each composition example having a thickness of 10 mm are 80%. % Are shown in Table 1.

The compositions of the examples are expressed in terms of the weight percentage of oxides when the cations contained in the glass are calculated as oxides, in which oxygen ions are partially replaced by fluorine ions which are partially described. ing. In addition, those in which the contents and components are changed within the limited range are described in seven compositions. A wavelength (τ80% (n) at which the internal transmittance of glass having a thickness of 10 mm is 80%, which is an index of transmittance in the ultraviolet region, is 80%.
For m)), first, a 10 mm thick internal transmittance was measured using a double beam type spectrophotometer, a 2 mm thick sample (glass) was inserted on the reference light side, and 1 mm on the sample light side.
This is performed by inserting a sample (glass) having a thickness of 2 mm and reading the transmittance at each wavelength. Table 1 shows the wavelength at which the internal transmittance of the glass of each composition example becomes 80% as a standard for comparison with the transmittance of the conventional glass in the ultraviolet region.

[0033]

[Table 1]

According to Table 1, the composition of Composition Example 1 is in terms of% by weight, P ₂ O ₅ is 71.6, SiO ₂ is 2.0, Al ₂ O ₃ is 16.4, K ₂ O is 6.7, CaO is 1.2, As ₂ O
₃ 0.1, F ₂ is 1.9. R ¹ ₂ O is K in this example
₂ O6.7, and R ² O is CaO1.2.

Next, the composition of Composition Example 2 is 63.9% by weight, P ₂ O ₅ is 63.9, SiO ₂ is 0.9, Al ₂ O ₃ is 5.0, B
₂ O ₃ is 0.8, BaO is 3.8, ZnO is 24.5,
As ₂ O ₃ is 0.2 and F ₂ is 0.9. In this example R ¹ ₂ O is not contained. Since R ² O is BaO and ZnO, the content is 28.3.

The composition of Composition Example 3 was 7% by weight and P ₂ O ₅ was 7%.
0.8, SiO ₂ is 1.6, Al ₂ O ₃ is 14.5, N
a ₂ O is 0.3, K ₂ O is 5.6, MgO is 0.5, C
aO is 3.8, SrO is 0.8, As ₂ O ₃ is 0.1,
F ₂ is 2.0. R ¹ ₂ O in this example Na ₂ O and K ₂
Since it is O, the content is 5.9, and since R ² O is MgO, CaO, and SrO, the content is 5.1.

The composition of Composition Example 4 was 7% by weight and P ₂ O ₅ was 7%.
4.7, SiO ₂ is 1.1, Al ₂ O ₃ is 17.1, L
i ₂ O is 0.2, K ₂ O is 3.3, CaO is 2.2, A
s ₂ O ₃ is 0.1 and F ₂ is 1.3. In this example, R
¹ ₂ O is 3.5 content for a Li ₂ O and K ^₂ O, R ₂ O is CaO2.2.

The composition of Composition Example ₅ is 5% by weight and P ₂ O ₅ is 5%.
1.0, 4.7 for SiO ₂ , 5.6 for Al ₂ O ₃ , K ₂
O is 15.4, CaO is 8.7, BaO is 6.0, Zn
O is 3.2, Sb ₂ O ₃ is 0.2, and F ₂ is 5.2. R ¹ ₂ O in this example is K ₂ O15.4, content for R ² O is CaO, BaO and ZnO is 17.9.

The composition of Composition Example 6 is P ₂ O ₅ of 7% by weight.
3.0, SiO ₂ is 1.8, Al ₂ O ₃ is 17.5, L
i ₂ O is 0.2, K ₂ O is 5.7, As ₂ O ₃ is 0.2.
1, F ₂ is 1.7. R ¹ ₂ O in this example is the content for a Li ₂ O and K ₂ O is 5.9, R ² O is not contained.

The composition of Composition Example 7 is such that P ₂ O ₅ is 7% by weight.
1.3, SiO ₂ is 1.7, Al ₂ O ₃ is 4.9, K ₂
O is 5.2, MgO is 14.4, CaO is 0.7, Sb
₂ O ₃ is 0.2 and F ₂ is 1.6. R ¹ ₂ O in this example
Is K ₂ O, the content is 5.2, and R ² O is M
Since it is gO and CaO, the content is 15.1.

The composition of the conventional crown phosphate glass (special phosphate crown glass PKS1 in the above-mentioned literature) is expressed in% by weight, P ₂ O ₅ is 70.4, Al ₂ O ₃ is 9.0, and B ₂ O ₃ is 4.0, K ₂ O is 11.6, MgO
Is 4.0 and As ₂ O ₃ is 1.0. R of this glass
¹ ₂ O is its content 11.6 K ^₂ O, R ₂ O is the amount contained in MgO is 4.0.

The glass of any composition of composition examples 1 to 7
The refractive index (nd) is in the range of 1.50 to 1.60, and the Abbe number (νd) is in the range of 60 to 75. Glass having such an optical constant is excellent in stability against devitrification and chemical durability. Also, 10
The wavelength at which the internal transmittance with a thickness of 80 mm is 80% is the wavelength (34) of the conventional glass (the conventional product in Table 1) in all the composition examples.
6 nm) and τ80% (nm)
Can be set to 330 nm or less, that is, 330 nm at the maximum. This indicates that the transmittance in the ultraviolet region has been improved as compared with the related art, and any of them is suitable for use in an optical system requiring high transmittance in the ultraviolet region. Among the glasses of these composition examples, particularly excellent ones are to be mentioned. In the glass of composition example 1, the wavelength (τ80% (nm)) at which the internal transmittance at a thickness of 10 mm becomes 80% is 319 nm.
It is.

Thus, in the present invention, the refractive index (nd) is in the range of 1.50 to 1.60 and the Abbe number (νd) is in the range of 60 to 75, and the ultraviolet light transmission is excellent. An optical glass which is stable against devitrification can be obtained.

[0044]

According to the optical glass of the present invention described above, the refractive index (nd) satisfies the range of 1.50 to 1.60 and the Abbe number (νd) satisfies the range of 60 to 75. In addition, an optical glass having excellent transmittance in the ultraviolet region can be obtained. Therefore, it can be used as an optical system that requires high transmittance in the ultraviolet region, for example, as a lens for a reduction exposure projector, a fluorescence microscope, or the like.

Claims (2)

[Claims] 1. A composition in weight percent of below _{P 2 O 5 50~80 SiO 2 1~5} Al 2 O 3 5~20 B 2 O 3 0~5 R 1 2 O 0~20 R 2 O 0~40 the as ₂ O ₃ or Sb ₂ O ₃ 0.1~0.5 F ₂ 1~5, provided that at least one 1 R ¹ ₂ O is selected from the group consisting of Li ₂ O, Na ₂ O and K ₂ O, or 2 of these
R ² O is composed of MgO, CaO, SrO, BaO and ZnO
Wherein F ₂ (fluorine) is an oxide in which some oxygen ions of the oxide are replaced by fluorine ions. And has an optical constant of a refractive index (nd) of 1.50 to 1.60, an Abbe number (νd) of 60 to 75, and is excellent in ultraviolet transmittance. An optical glass characterized in that: 2. The optical glass according to claim 1, wherein an 80% value of a 10 mm internal transmittance is 330 nm or less.